The world does not revolve around you, teens are often told. Indeed it doesn’t, as they are reminded every school-day morning when disabling their alarms. The average start time for public high schools, 7:59, requires teens to get up earlier than is ideal for their biological clocks, meaning many teens disrupt their natural sleep patterns every school day.

The world, apparently, does not revolve around parents either. Their lives also tend to be mismatched with school-day schedules, which usually end a good two hours before the typical American workday does. As Kara Voght recently wrote in The Atlantic, that leaves a daily gap of unsupervised time for many children, forcing their parents to find affordable care for their kid or to adjust their own working schedule.

It’s not entirely clear who the school day does revolve around. The schedules that dictate most of American K-12 life descend from times when fewer households had two working parents. The result is a school day that frazzles just about everybody. But a few changes could mitigate that frazzling significantly. “I don’t know about making everyone perfectly happy,” says Catherine Brown, the vice president of education policy at the Center for American Progress, a left-leaning think tank. “But I think that we could get much closer to optimizing for students, parents, teachers.” The school day, Brown says, could be improved in two main ways: It could start later, and it could go longer.

Half past eight—the target for many start-school-later advocates—is actually still earlier than would be totally ideal. Kyla Wahlstrom, a lecturer at the University of Minnesota who conducted the first study examining the effects of later start times on high schoolers back in the late 1990s, told me that, taking only teens’ sleep needs into account, the best start time would be around 9:00 or 9:30; that would give them the optimal amount of time to sleep and get ready. “8:30,” she says, “is a compromise that allows more sleep, but does not impinge on the after-school activities.”

In the 20-plus years since Wahlstrom conducted that first study, hundreds of schools have moved back their start times, according to the advocacy group Start School Later, which does its best to count in absence of an official government tally. The group’s cause has gained momentum as the American Academy of Pediatrics (in 2014), the Centers for Disease Control and Prevention (in 2015), and then the American Medical Association (in 2016) recommended that middle and high schools start no earlier than 8:30, citing sleep deprivation’s negative effects on students’ health and academics. A California state bill currently awaiting the governor’s signature would require most middle and high schools to start no earlier than 8:30, which could affect the sleep schedules of millions of teens; still, earlier start times remain the norm nationwide. (And worldwide: “Although we don’t have comparative data, I have observed that starting [the] school day early is not an exception,” says Yuri Belfali, the head of early childhood and schools at the OECD, a group representing 36 mostly wealthy countries. “For example, it is not unusual that [the] school day starts at 7:30 a.m. or earlier in Singapore and other Asian countries, or in Brazil.”)

The rationale for the second school-day change—go longer, for working parents’ sake—is just as straightforward. More than a thousand American schools have extended their school days by an hour and a half, and many charter schools, which have more latitude than normal public ones, have school days that end closer to when work does. But no movement has formed around altering the school day in this way; there’s no advocacy group called Make School Longer (a tougher sell to students, probably) and America’s respected medical groups seem unlikely to announce a stance on how to make it easier for parents to juggle work and their kids’ schooling.

I asked Brown what her ideal school-day schedule would look like, if she could start from scratch. She told me it’d start later, at 8 or 8:30—not just for teens, but also for younger kids. The day would end at 5 or 5:30, but the extended day's extra hours wouldn't be spent solely in the classroom. Brown says she’d “have a period in the afternoon where they’re doing creative activities and they’re doing physical activities, sports, arts, music—I would bake all that stuff into the day, as opposed to the after-school being plopped on, disconnected from the rest of the learning goals of the school.” (In Brown’s hypothetical ideal school day, teachers wouldn’t be asked to work longer days, but would instead work in shifts.)

Today’s standard 6.5-hour school day looks quite different. “I’m not pretending this is a utopia,” Brown says. “I’m just repeatedly struck, as a mother and as an education policy wonk, [by] how schools don’t often consider the needs of parents' work schedules when they’re designing all kinds of policies.”

Early start and end times have remained the norm in part because inertia is powerful—it’s “a problem in the sense that this is how we’ve always done it, so this is the way we’ll keep doing it,” Brown says. And the obstacles to changing it usually fall under three general categories: sports, buses, and funding.

“When there’s a weird practice in American education and you don’t know why, if you say ‘sports,’ you’ll be right about 75 percent of the time,” says Jonathan Zimmerman, a professor at the University of Pennsylvania’s Graduate School of Education. A lot of the pushback against moving back school start times, he notes, comes from coaches, players, and parents who worry that the change would eat into precious practice and game time. For instance, when an education board on Long Island sought public comments last year on the possibility of moving school start times back, some parents fought the change passionately. “Every single contest that we play next year will be affected by a 3 o’clock [end] time,” one father warned. “Every practice and every single game.”

Buses are the second issue. Brown says many districts don’t have enough of them to move every kid at once, so fleets works in cycles, staggering pick-up and drop-off times based on age. High schoolers are usually first—parents tend not to want younger children waiting in the dark—then middle schoolers, then elementary schoolers.

This arrangement dates back to four or five decades ago, and teens’ sleep needs were not on its architects’ minds. Back then, buses were a way of getting kids to school amid new, pedestrian-unfriendly sprawl (most kids used to just walk), but also of assuaging fears that walking to school alone was dangerous. And as many districts bought buses and hired drivers, they kept fleets only as big as absolutely necessary, to save money. Increasing spending on buses and drivers is no small thing when many schools are already dealing with slashed budgets; transportation costs might rank as a lower priority at schools with, say, outdated textbooks or run-down facilities.

Which connects to the third common category of opposition to changing the school day: concerns about funding a longer day. Increasing the amount of time that schools operate each day, as Brown favors, would cost money. She cites this as another reason that changing the school day is difficult. “Our schools haven’t even recovered from the 2008 recession,” Brown says. “More than half of states are funding their school systems at a lower level than they were in 2008.”

Still, she says, there are ways for schools to adapt. As she outlined in a 2016 report, there are a few ways that schools could apply for federal funding to extend the school day under the Every Student Succeeds Act of 2015. Also, she says schools could have outside enrichment programs step in for a period of the day.

At any rate, many parents already are paying for the fact that the school day ends before the workday, in the form of childcare or extracurriculars. “We’re effectively asking parents right now to subsidize the school day,” Brown said.

There is probably no such thing as a school-day schedule that satisfies every constituency. Keep start times early, and teens don’t get the sleep they need. Make start times later, and people involved in sports and other extracurriculars complain, and transportation costs go up. Keep school days the usual length, and working parents are in a jam. Make school days longer, and both students and teachers might dread the added time. But still, it seems an amended school-day schedule could make a lot of these people collectively less unhappy than they are now.

Kids have to go somewhere while their parents work, and it’s going to get funded one way or another. Ansley Erickson, an associate professor of history and education at Columbia University’s Teachers College, told me about another model, from the early-20th century in New York City, when a lot of mothers worked outside the home. “There was a lot more time that kids spent unsupervised, and there were also a lot more intentional spaces in the city where kids could be and be supervised that were not school spaces,” she said. Some of these were private (after-school programs run by churches or community centers) and some were public (libraries; playgrounds staffed with supervisors to watch over children). There are, as history indicates, other ways of looking after kids when they aren’t in classrooms that could serve as a model for reimagining their schedules. It would just take creativity, some reallocating of money, and most of all a collective resistance of inertia.

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Joe Pinsker is a staff writer at The Atlantic, where he covers families and education.